Capacitive touch screen stylus

Abstract

In some embodiments, a stylus for providing input to a capacitive touch screen, having a tip including or consisting of conductive felt, which provides a deformable conductive surface for contacting the touch screen. The tip is produced by felting base fibers (which are typically non-conductive) with conductive fibers. In other embodiments, a capacitive touch stylus having at least a first mode of operation and a second mode of operation, and including at least one conductive tip and switched circuitry (preferably, passive circuitry) including at least one switch biased in a default state indicative of the first mode of operation but switchable into a second state indicative of the second mode of operation in response to movement of the tip (typically, in response to exertion of not less than a threshold force on the tip). In some embodiments, a stylus having a conductive tip (e.g., a conductive, felted tip) and including switched circuitry (preferably, passive circuitry) having a first state which couples a capacitance to the tip, where the capacitance is sufficient to allow a capacitive touch screen device to recognize (as a touch) simple contact of the tip on the screen of the touch screen device, and a second state which decouples the capacitance from the tip, thereby preventing the touch screen device from recognizing (as a touch) simple contact of the tip on the screen.

1 . A stylus comprising:
 a felted tip having a deformable conductive surface for contacting a capacitive touch screen, the tip having a contact area sufficient in magnitude and the tip is coupled to a capacitance sufficient in magnitude to cause the capacitive touch screen to recognize a touch by the tip; and   a structure supporting the tip and supporting an application of force to deform the tip conductive surface.   
     
     
         2 . The stylus of  claim 1 , wherein the structure is a conductive shaft coupled to the tip. 
     
     
         3 . The stylus of  claim 1 , wherein the tip is semi-rigid. 
     
     
         4 . The stylus of  claim 1 , wherein the tip is made from a blend of conductive and non-conductive fibers. 
     
     
         5 . The stylus of  claim 1 , wherein the tip comprises conductive fibers and base fibers that have been felted with the conductive fibers. 
     
     
         6 . The stylus of  claim 5 , wherein the base fibers are wool fibers. 
     
     
         7 . The stylus of  claim 5 , wherein the conductive fibers are carbon fibers. 
     
     
         8 . The stylus of  claim 5 , wherein the conductive fibers are fibers coated with metal. 
     
     
         9 . The stylus of  claim 5 , wherein the conductive fibers are fibers coated with carbon. 
     
     
         10 . The stylus of  claim 5 , wherein the conductive fibers have electrical resistivity such that the combined resistance and capacitance of the tip, when the tip is coupled to the capacitance, in aggregate, is sufficient to cause the capacitive touch screen to recognize a touch by the tip, and the capacitance of the tip alone is insufficient to cause the capacitive touch screen to recognize a touch by the tip. 
     
     
         11 . The stylus of  claim 5 , wherein the conductive fibers have electrical resistivity not more than on the order of 10,000,000 ohms-cm). 
     
     
         12 . The stylus of  claim 1 , wherein the tip has an at least substantially bullet-like shape when in an undeformed state. 
     
     
         13 . The stylus of  claim 1 , wherein the tip has an at least substantially hemispherical shape when in an undeformed state. 
     
     
         14 . The stylus of  claim 1 , wherein the structure includes a conductive shaft, and said stylus also includes:
 switched circuitry selectable to provide a configuration state that forms a low impedance path that couples an additional amount of capacitance to the tip, the combined capacitance sufficient to allow the capacitive touch screen to recognize a touch by the tip, and wherein the switched circuitry in an alternate state does not couple to sufficient additional capacitance to the tip to allow the capacitive touch screen to recognize a touch by the tip.   
     
     
         15 . A system comprising:
 a capacitive touch screen device comprising:   a capacitive touch screen surface;   a controller that defines a touch event on the capacitive touch screen surface by the touch event having at least a threshold contact area value and a threshold change in local capacitance value; and,
 a stylus comprising: 
   a tip with a conductive surface coupled to a capacitance, the tip and capacitance switchable from a first state in which the tip coupled to the capacitance stimulates the capacitive touch screen surface to a second state in which the tip does not stimulate the capacitive touch screen surface; and,   support structure for supporting the application of the stylus tip to the capacitive touch screen surface.   
     
     
         16 . The stylus of  claim 15 , wherein said tip is a felted tip that includes base fibers and conductive fibers felted with the base fibers. 
     
     
         17 . The stylus of  claim 15 , wherein the tip coupled to the capacitance is passively switchable between the first state and the second state. 
     
     
         18 . The stylus of  claim 15 , wherein the structure includes a conductive shaft, and said stylus also includes:
 switched circuitry selectable between the first state that forms a low impedance path that couples an additional amount of capacitance to the tip, the combined capacitance sufficient to allow the capacitive touch screen to recognize a touch by the tip, and wherein the switched circuitry in the second state does not couple to sufficient additional capacitance to the tip to allow the capacitive touch screen to recognize a touch by the tip.   
     
     
         19 . The stylus of  claim 18 , wherein the switched circuitry also includes a stylus audio port set, including at least one audio port configured to be coupled to an audio cable. 
     
     
         20 . The stylus of  claim 19 , wherein the stylus audio port set includes at least one audio input port, and at least one audio output port. 
     
     
         21 . The stylus of  claim 19 , wherein the stylus audio port set has a state indicative of contact between the tip and an object external to the stylus. 
     
     
         22 . The stylus of  claim 19 , wherein the stylus audio port set has a state indicative of pressure exerted by an object on the tip. 
     
     
         23 . The stylus of  claim 19 , wherein the switched circuitry includes at least one sensor, and the stylus audio port set has a state indicative state of the sensor. 
     
     
         24 . The stylus of  claim 19 , wherein the stylus audio port set has a state indicative of state of at least one switch of the switched circuitry. 
     
     
         25 . The stylus of  claim 19 , wherein the audio cable includes left and right output channel connectors, a microphone channel connector, and a ground connector, and the stylus audio port set is configured to be coupled to an end of the audio cable, such that another end of the cable can be coupled to a host audio port set of a capacitive touch screen device. 
     
     
         26 . In a system having
 a capacitive touch screen device comprising:
 a capacitive touch screen surface; 
 a controller that defines a touch event on the capacitive touch screen surface by the touch event having at least a threshold contact area value and at least a threshold change in local capacitance value; and, 
   a stylus comprising:   a tip with a conductive surface coupled to a capacitance, the tip and capacitance switchable from a first state (tip down) in which the tip coupled to the capacitance stimulates the capacitive touch screen surface to a second state (tip up) in which the tip does not stimulate the capacitive touch screen surface,   a method comprising:   a) transmitting from the stylus to the capacitive touch screen device, a signal associated with a transition in the stylus from the tip up state to the tip down state and assigning a time T 1  to that signal;   b) on the capacitive touch screen device, gathering all touch event data, including touch events, if any, associated with contact between the stylus tip in the tip down state and the capacitive touch screen;   c) for gathered touch events that occurred within a predetermined time interval relative to T 1 , creating a collection of unclassified touch event data; and   d) processing the collected unclassified touch event data to differentiate touch events likely caused by movement of the stylus tip in the tip down state from touch events likely caused by touches of the capacitive touch screen by objects other than the stylus.   
     
     
         27 . A stylus, including:
 tip with a deformable conductive surface; and   switched circuitry having a first state which couples additional capacitance to the tip, where the combined capacitance is sufficient to cause a change in a local electric field of a capacitive touch screen device sufficient to allow the device to recognize, as a touch, simple contact of the tip on of the capacitive touch screen device, wherein the switched circuitry also has a second state which decouples the additional capacitance from the tip, and the capacitance of the tip alone is insufficient to cause the capacitive touch screen device to recognize a touch by the tip.   
     
     
         28 . The stylus of  claim 27 , wherein the conductive tip is a conductive, felted tip that is deformable, and includes base fibers and conductive fibers felted with the base fibers. 
     
     
         29 . The stylus of  claim 27 , wherein the switched circuitry is passive switched circuitry. 
     
     
         30 . The stylus of  claim 27 , wherein the capacitance is a capacitive load external to the stylus. 
     
     
         30 . The stylus of  claim 27 , wherein the capacitance is internal to the stylus. 
     
     
         31 . The stylus of  claim 27 , wherein the switched circuitry includes at least one switch biased in a default state which couples the additional capacitance to the tip but is switchable in response to movement of the tip into a second state which decouples the capacitance from said tip, where the switch is coupled to the tip in the default state. 
     
     
         32 . The stylus of  claim 27 , wherein the switched circuitry includes at least one switch biased in a default state which decouples the additional capacitance from the tip but is switchable in response to movement of the tip into a second state which couples the additional capacitance to said tip, where the switch is coupled to the tip in the second state. 
     
     
         33 . The stylus of  claim 27 , wherein the switched circuitry also includes a stylus audio port set, including at least one audio port configured to be coupled to an audio cable. 
     
     
         34 . The stylus of  claim 27 , wherein the switched circuitry includes at least one variable circuit element whose state is determined by sensor input. 
     
     
         35 . The stylus of  claim 34 , wherein the switched circuitry also includes an audio port set, including at least one audio port configured to be coupled to an audio cable, and the switched circuitry is configured to assert to the audio port set a response signal indicative of state of the variable circuit element.